Papermaking press with inflatable rolls having thin deformable outer shells

ABSTRACT

An extended nip is created in a papermaking roll press assembly whereby the rolls are provided with thin, deformable outer shells and fixed, rigid seal plates in the ends of the shells for holding pressurized fluid within the shells. Separately inflatable annular seals provided between the fixed, end seal plates and the shells also help prevent escape of fluid from within the shells. Support beams extending the length of the roll shells opposite the nip have perforations therein for allowing fluid to pass between the beams and the rotating outer shells of the rolls for reducing sliding friction.

United States Patent [191 Mohr et al.

[451 Apr. 16, 1974 PAPERMAKING PRESS WITH INFLATABLE ROLLS HAVING THIN DEFORMABLE OUTER SHELLS [75] Inventors: William C. Mohr, Rockford; Carl J.

Francik, Roscoe, both of I11.

[73] Assignee: Beloit Corporation, Beloit, Wis.

[22] Filed: Mar. 8, 1972 [21] Appl. No.: 232,820

[52] US. Cl 162/358, 29/113 AD, 100/211,

162/305 [51] Int. Cl. D211 3/08 [58] Field of Search 162/358-360,

162/361, 305, 205, 276, 206; 100/211, 170, -l62 B; 29/113 R, 113 AD, 116 AD [56] References Cited UNITED STATES PATENTS 3,586,602 6/1971 Schmidt 162/205 X 3,266,561 8/1966 Beachler et al. 100/162 B 3,120,174 2/1964 Answorth.... 100/170 3,146,160 8/1964 Kankaanpaa [62/276 X 3,293,121 12/1966 Martin 162/358 3,269,893 8/1966 Rejecki 162/358 X Primary Examiner-S. Leon Bashore Assistant Examiner-Richard H. Tushin Attorney, Agent, or Firm-Hill, Sherman, Meroni, Gross & Simpson [5 7] ABSTRACT An extended nip is created in a papermaking roll press assembly whereby the rolls are provided with thin, deformable outer shells and fixed, rigid seal plates in the ends of the shells for holding pressurized fluid within the shells. Separately inflatable annular seals provided between the fixed, end seal plates and the shells also help prevent escape of fluid from within the shells. Support beams extending the length of the roll shells opposite the nip have perforations therein for allowing fluid to pass between the beams and the rotating outer shells of the rolls for reducing sliding friction.

9 Claims, 5 Drawing Figures iPABERMAKINGBRESS =WI'IIHJNFLATABLE r-ROIJIJSlHAVING :THIN DEFORMABLE OUTER SHELLS .BACKGROUNDQF THEINVENTION The invention. relates to improvements in roll presses and.moreparticularlyto a; press for use in a mechanism such as a, paper making machine, whereinthepress is .capable of providing anextended orelongate nip.to subject the:trave1ing web-to a longer pressing time to a permit. overcoming, of .the resistant: hydraulic pressure .within the web andobtaindmproved water removal fromthe web and-the irnprovedeffectsof an extended nip,press.

ln thecopending applicationofi-Busker and Francik,

-Ser. 'No. l9 3,272,.:the ,principles andadvantages of pressing apaperwebfor an extendedrperiod oftime, andthe advantages; thereof, are discussedpln the.presentstructure'the principles of an extended time nip are utilized in a structureaffording advantagesover prior artarrangements. 1

Aswill-beappreciatedlfromtheteachingsofith dis closure, thefeatures ofzthe invention maybe employed in thedewatering of otherforms of webs'thana paper web in apapermakingtmachine.However, for.convenience, apreferred.embodimentofthe invention will bedescribed. in the environment of apaper making machine which ,conventionally' forms. a web by depositing atslurry. of pulp:fibers.on artraveling fabric oriwirebelt,

transfersthe web '10 a press section where the web I passesthrough anumber ofpress nips formed between rollcouples, and the web thenpasses over a series of heated. dryerdrums and, usuallythrough. a. calender and thisiswound on;theroll. T he presentstructure forms the entirepress sectionandtakes the ,plaeeof other .forms of press sections :heretofore available. Many modifications cambe made inthis typeofroverall mavwatertofiber. plus water) .and'leaves the press section with approximately 60;per.cent moisture,withthe remaining moisture having .to ;be removed by thermal evaporation inthe dryer section asztheweb passes over a series of heateddryerdrums. :Because of .various inherentlimitations in'theoperation of rollcouples formingpressnips for the press section in a conventional .paper making machin'e,.only a .given vamount of water .can be-removedrinreaeh nip and, therefore, in a conventional paper making machine,,a seriesof three press nipsareusually employed. It hasbeen found impracticalto attempt to remove a significant amount of additionaLwater by increasing the number of press nips, although the furtherremoval of water by, Pressing .can greatly reduce the ,expenseand size of the dryer section. It isestimated that if the amount of .water removed in the press section .can vbeuincreased so that .the wet basis moisture is vdecreased from 60 percent to 50 per cent, the length of thedryersectioncan be reduced by one-third. This is significantin .a typical 3,000 feet per minute newsprint machine which employs approximately 60 dryer drums. This significance can be appreciated in considering that the dryer drums are each expensive to construct and to operate and require the provision ofsteam fittings and a supply ofsteam for each drum. The relativeimportance of the removal of water in the press section is further highlightedibythe fact that one of the most important economic considerations in justifying asatisfactory return on=investment in the operation of a paper making machine is to obtain the-highest speed possible consistent with good paper properties and the removal of more water through bet- .ter pressing will shorten the necessary time inathedryer section and permit higher speeds and greater production rates.

It is accordingly an object of the present invention to provide an improvement in a paper machine which makes it possible to remove an increased amount of water in the pressing operation and makes itpossible to provide a press section having fewer pressing nips of a unique elongated or extended nature which do not have the performance limitations of conventional .roll couple presses and which require far less space in terms of requirements as to the overall length of the press section. By increasingthe amount of water'removed-from the web in the press section, increased speeds are possible with existing equipment, i.e., a given length of dryer section can operate at higherspeeds since it is required to remove less water. Also, new equipment ean be constructed requiring less overall machine length and expense.

The present'invention employs a principle which may be referred to as theextended nip concept-wherein the time the web is subjected'to a pressing action is greatly extended, i'.e., a single pressing is provided'having a residence time which exceeds that of the timeof theweb in a number of conventional roll ,rcouple press nips. With the reduction to a single pressingoperatiomxthe compound effects of rewettingthe web as it'leaves a plurality of nips are avoided.

A factor whichpresently limits water removal from paper by mechanical wetpressing is the flow property of water within the paper sheet. lt hasbeen foundthat other factors are not of dominant significance, for example, the effects of the moisture in the felt-which-trav- ,els with the web are small. it has been found further that the length of time'that the web isin the nip, in other words the residence in the nip, can have a significant effect in overcoming the difficulties createdby the flowrproperties of the water within the sheet.lt has also been found that merely by increasingthe residence time of the web in the nip, the water content of the sheet coming out of the press can be decreased so that the web will 'have 46 per cent dryness rather than 40 per cent dryness with other variables remaining constant. As is evident, the residence time of a web in a conventional roll couple press nip is limited and can only be increased by decreasing the speed of travel of the web, or can be increased slightly by increasing the diameter of .the press rolls, but these factors are indeed limiting. It has been found, for example,that by applying a 1,300 pound per square inch pressure on a web for 5 minutes, a moisture level of less than 30-per cent can be attained. Yet, under the dynamic short term mechanical pressing of a paper machine press section using roll couples, even with a-plurality of nips, agreat deal of effort is required to maintain moisture levels below 60 per cent.

It has been found that significant decreases in moisture removal occur at higher speeds and that a loss in dryness of over per cent is experienced in going from 300 feet per minute to l,000 feet per minute with typical press loadings in a suction press. It has been found that a hydraulic pressure or wedge develops during the passage of the wet mat through the press nip. The hydraulic pressure that develops subtracts from the applied load and reduces the mechanical compacting pressure. The result is a loss in dryness. As the machine speed increases, the compacting rates are higher resulting in higher hydraulic pressures within the paper mat. These hydraulic pressures react against the pressure of the rolls and prevent the moisture from being squeezed from the web. The exact value of hydraulic pressure is difficult to determine either by direct measure or analysis because of the space and speeds involved. It is believed, however, that hydraulic pressure predominately determines press performance on machines operating at high speeds. Accordingly, the instant invention relates to avoiding disadvantages encountered with high speed press nips of the conventional type used in most commercial applications today, and provides a substantial increase in residence time within a press nip to allow time for flow to occur within the mat and for the hydraulic pressure to dissipate. The principles of extended nip or extended time pressing are further reviewed in the aforementioned copending application.

An object of the present invention is to provide an improved press which avoids disadvantages of the prior art and which obtains an extended nip pressing action capable of achieving the advantages provided by subjecting a web to a pressing action over an extended length of time.

A further object of the invention is to provide an improved pressing mechanism which is capable of performing the complete mechanical pressing action in a paper making machine, avoiding the necessity of having to provide a plurality of conventional press nips.

Other objects, advantages and features will become more apparent to those versed in the art as will other forms of the invention from the following teachings of the principles of the invention in connection with the disclosure of the preferred embodiments'thereof in the specification, claims and drawings in which:

DESCRIPTION OF THE DRAWINGS FIG. 1 is a somewhat schematic end elevational view of a press constructed and operating in accordance with the principles of the present invention;

FIG. 2 is a fragmentary somewhat schematic side elevational view showing a press;

FIG. 3 is a fragmentary sectional view taken substantially along line III-III of FIG. 1;

FIG. 3a is a fragmentary sectional view illustrating another form of seal; and

FIG. 4 is a fragmentary sectional view taken substantially along line IVIV of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As illustrated in FIGS. 1 and 2, the press includes first and second opposed roll members and 11. These roll members are elongate having a width somewhat wider than the web W passed between them. Each of the roll members is in the form of a thin, flexible roll shell which may be formed of metal, plastic or rubber,

sufficiently flexible to deflect along the length of the extended nip N.

The roll shells 10 and 11 are pressurized in their interior to apply a pressure along the extended nip region N which pressure is substantially uniform along the axis of the roll shells. The roll shells are provided with means for sealing their ends, and may have integral end caps, although preferably are provided with stationary seals. Integral end caps will require a deflection or distortion of the material at the area of the nip N as the rolls rotate, whereas the stationary end seal will be shaped in accordance with the profile shown in FIG. 1. The form of stationary end seal is shown in FIG. 3 and will be described later herein.

For pressurizing the interior of the roll shells, fluid pressure inlet tubes 14 and 15 are connected to the shells at their axis. Fluid such as pressurized air is supplied from a suitable source controlled to obtain uniform pressure. The structure would operate with one of the opposing rolls being a rigid cylindrical metal roll and the other being formed of a thin, flexible shell. With one of the rolls being solid and the other having a flexible outer shell, the nip line would have to follow the arcuate contour of the rigid roll. A preferred form incorporates both opposing rolls being formed of a thin, flexible shell in order to obtain essentially a straight line N. In the form illustrated, both roll shells 10 and 11 are pressurized with the same interior fluid pressure.

To prevent the rolls from deflecting away from each other along their lengths, they are backed by the supporting means extending along the length of the rolls, preferably in the form of support beams 16 and 17 for the rolls l0 and 11, respectively. The support beams are constructed with substantial strength so that they exhibit minimum deflection while resisting the loads from the two opposed roll shells away from each other. In some instances where a long nip is employed and the nip forces are high, the support beams may be provided with reinforcing means to prevent their deflection. These reinforcing means for the beam may take the form of bending members cantileverly located at the ends of the beam to apply counteracting force and bend the beams in such a manner that they are bent downwardly at their centers to counteract the greater moment of deflection of the rolls at their center.

To permit rotation of the rolls at relatively high speed while providing means for resisting the pressure loads, a fluid bearing means is provided between the rolls and the beams. The beams are preferably formed with an arcuate concave facing surface 18 and 19 for the beams 16 and 17 respectively. These surfaces extend for approximately to of the arc of the rolls. A fluid bearing is provided between the surfaces 18 and 19 and the outer surfaces of the rolls. This fluid bearing is provided with air or other fluid introduced between the outer surface of the roll shell and the inner surface of the beam such as by openings as shown in FIG. 4.

By passing a felt 20 through the nip with the web, fluid pressed from the paper web will be received by the felt. In some operations, it may be desirable to provide two felts so that the paper web W is sandwiched therebetween. Means will be provided to remove moisture from the felts after separation from the paper web and on a return path to provide a desired condition of reduced felt moisture when again entering the nip.

FIG. 3 illustrates the form wherein stationary end seals 21 and 22 are provided within the flexible roll shells 10 and 11. The roll shells are backed by beams such as 16. The stationary end seals 21 and 22 will be shaped in accordance with the profile shown in FIG. 1. The end seals will be shaped so as to provide a nip length of optimum size, although if a longer or shorter nip is to be desired, the shape of the end seals 21 and 22 can be altered. For improved sealing, inflatable annular seals 23 and 24 may be provided between the stationary plates 21 and 22, and these seals provided with a suitable pressurizing means, not shown. Pressure supply lincs such as 25 will be provided for pressurizing the interior of the roll shells l and 11'.

In FIG. 3a the flexible roll shell 31 has an end seal plate 30 carrying a hollow resilient inflatable seal 32 on its periphery. This seal is connected with a fluid pressure line 33 which inflates the seal to the pressure necessary to prevent the escape of fluid from within the roll shell.

In the arrangement of FIG. 4, the inner surface of a support beam 16" is shown. A plurality of perforations or openings 26 are provided in the concave inner surfaces of the'beam 16', and pressurized air supply lines such as 27 lead to these perforations to generate a supporting film of air between the rollshell and the beam in order to provide a fluid bearing. This will permit rotation of the roll shells without wear between their surfaces and the bearing. The outer surface of the roll shell, of course, will be smooth so as to not create any marking on the paper web.

In most instances anannular end drive will be provided for driving the roll shells, but one roll shell might be driven through contact with the paper web and felt. The resistance to rotation will be relatively small in view of the substantially frictionless support afforded by the fluid bearings. Changes in nip pressure may be obtained during operation by changing the pressure of the fluid within the roll shells. Thus, different operating conditions such as different quantities of moisture within the web, and the handling of webs of different characteristics may be accommodated by the same mechanism.

We claim as our invention: l. A press mechanism for pressing liquid from a traveling web comprising in combination,

first and second opposed roll members mounted for rotation about parallel axes and forming an extended pressing nip therebetween for receiving a traveling web and expressing liquid therefrom in the pressing zone defined by the nip, at least one of said rolls having a thin deformable outer shell deforming at the nip to extend said pressing zone,

means for receiving water passing with said web through said nip,

fixed rigid seal plates in the ends of the shell for holding pressurized fluid within the shell,

means for pressurizing the interior of said roll shell for obtaining a predetermined pressure in the nip,

a supporting means extending along the length of the outer surface of said one roll opposite the nip preventing substantial deflection of the roll axis away from the nip,

and means for reducing sliding friction between said supporting means and said roll.

2. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim I, wherein said supporting means is in the form of an elongate beam extending parallel to the roll and in supporting engagement therewith.

3. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 2, wherein said means for reducing sliding friction includes means for introducing a fluid between said beam and said roll so that a fluid bearing is provided supporting and lubricating the roll relative to the beam for accommodating high speed operation.

4. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 3, wherein said beam has an arcuate inner surface extending over a substantial circumferential area of the roll and said surface is provided with a plurality of perforations with passages leading to the perforations and the fluid for the bearing is delivered to said passages under pressure for providing a fluid bearing between the roll and the beam which comprises said means for reducing sliding friction.

5. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 3, wherein said means for introducing fluid is constructed to introduce air between the beam and roll.

6. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 1, and including stationary end seals fitted within the ends of said deformable outer shell so that the shell rotates relative to the seal and the escape of fluid from within the shell is prevented by said seal.

7. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 6, wherein said seal is hollow and resilient to be inflatable relative to the shell for controlling the operation of the seal.

8. A pressmechanism for pressing liquid from a traveling web constructed in accordance with claim 1, wherein each of said rolls has a thin deformable outer shell and each is provided with a supporting means extending along its length and preventing deflection of the rolls away from the nip.

9. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 8, wherein said means for receiving water comprises a felt. 

1. A press mechanism for pressing liquid from a traveling web comprising in combination, first and second opposed roll members mounted for rotation about parallel axes and forming an extended pressing nip therebetween for receiving a traveling web and expressing liquid therefrom in the pressing zone defined by the nip, at least one of said rolls having a thin deformable outer shell deforming at the nip to extend said pressing zone, means for receiving water passing with said web through said nip, fixed rigid seal plates in the ends of the shell for holding pressurized fluid within the shell, means for pressurizing the interior of said roll shell for obtaining a predetermined pressure in the nip, a supporting means extending along the length of the outer surface of said one roll opposite the nip preventing substantial deflection of the roll axis away from the nip, and means for reducing sliding friction between said supporting means and said roll.
 2. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 1, wherein said supporting means is in the form of an elongate beam extending parallel to the roll and in supporting engagement therewith.
 3. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 2, wherein said means for reducing sliding friction includes means for introducing a fluid between said beam and said roll so that a fluid bearing is provided supporting and lubricating the roll relative to the beam for accommodating high speed operation.
 4. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 3, wherein said beam has an arcuate inner surface extending over a substantial circumferential area of the roll and said surface is provided with a plurality of perforations with passages leading to the perforations and the fluid for the bearing is delivered to said passages under pressure for providing a fluid bearing between the roll and the beam which comprises said means for reducing sliding friction.
 5. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 3, wherein said means for introducing fluid is constructed to introduce air between the beam and roll.
 6. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 1, and including stationary end seals fitted within the ends of said deformable outer shell so that the shell rotates relative to the seal and the escape of fluid from within the shell is prevented by said seal.
 7. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 6, wherein said seal is hollow and resilient to be inflatable relative to the shell for controlling the operation of the seal.
 8. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 1, wherein each of said rolls has a thin deformable outer shell and each is provided with a supporting means extending along its length and preventing deflection of the rolls away from the nip.
 9. A press mechanism for pressing liquid from a traveling web constructed in accordance with claim 8, wherein said means for receiving water comprises a felt. 